Putting is a critical aspect of the game of golf. While each golfer tends to possess his own unique style of putting, some fundamentals are universally recognized as being essential to successful putting technique. The golfer's head and eyes must be positioned directly over the ball in the vertical plane in line with the path the putter head will travel toward its target. The putting stance with the golfer "eyes over the ball" assists in accurately aligning the path of the putter head in the direction of the cup. A golfer generally relies on his own visual perception to insure that his stance positions his "eyes over the ball."
In addition, the golf ball must be contacted at the center of gravity or "sweet spot" of the striking face of the putter head, and the sole of the putter head must be parallel to the putting surface. The angle of the putter's shaft determines whether the sole of the putter head is parallel to the putting surface. The position of a golfer's hands relative to a horizontal plane generally at or about his belt line can vary the angle of the putter shaft thereby affecting the position of the putter head with respect to the putting surface. If the golfer's hand position is too low relative to this plane, the toe of the putter head will be raised higher than the heel and the sole of the putter head will not be parallel to the putting surface. If the golfer's hand position is too high relative to this plane, the heel of the putter head will be raised higher than the toe and again the sole of the putter head will not be parallel to the putting surface. If the sole of the putter head is not parallel to the putting surface upon contact with the ball, its center of gravity shifts, which generates torque in the putter head.
A variety of putter heads have been developed which assist the golfer in visually determining the proper position of the putter head with respect to the ball, target line and putting surface. Some putter head designs focus on heel and toe weighting to counter off-center hits. Many conventional putter heads have markings, lines or grooves that assist the golfer in aligning the ball at the "sweet spot" of the striking face and aligning the striking face perpendicular to the target line. U.S. Pat. No. 3,880,430 issued to McCabe discloses a putter that allows the golfer to visually determine if the sole of the putter head is parallel to the putting surface. The McCabe putter includes a pair of laterally spaced parallel markings placed on a horizontal flange that extends rearwardly from the striking face and a rearward extension spaced above the flange. To achieve proper putter head alignment and positioning, the golfer must visually center the rearward extension between the two parallel markings. Consequently, the accuracy of this positioning method is dependent on the golfer's own perception of whether the extension is centered between the markings. Naturally, visually centering the extension between the markings is more difficult as the width of the extension and the lateral spacing between the markings increases. Errors in accurately centering the extension between the two markings result in the improper positioning of the putter head and mishit putts.